Weight Weenies

Well said Pez... they look CNC from billet to me but as you said it's difficult to know if there was post machining on a forged or cast part.

No offense taken, it wasn't meant to stir the pot or anything, please don't get me wrong. Just something i noticed. And when i hear CNC machined from chinese products and see this type of finish I simple put one and one together.

The finish on both pictures you provide are giving me a molded impression (most likely with a CNC machined opp.)

Take a look at products like Hope for example. It's easy to see these parts are CNC machined. I'm not saying molded is bad per definition. Not saying the brakes are poor in quality either, but again, CNC machined and (relative cheap) chinese products and this type of finish? that makes me wonder. That's why i say 'cheap chinese mould')

This is cnc machined, most parts from 7075T6 with a proper finish IMHO

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I understood that the rule of thumb was that cast alloy is stronger than CNC'd - This was mainly in the context of stems but assume would apply to items(?).
That not withstanding IMO my KCNC brakes are CNC manufactured (by Ken's CNC business) based on the sharpness of edges etc.- might be wrong.
From the images the new KCNC brakes look like they are not machined quite as well with visible roughness on the inside face of the cable stop lever arm.

Just in case you didn't know...KCNC is based in Taiwan, not China. They have patents for various of their products and the quality is well beyond some of the more comon chinese parts you see around. JFYI...

Tool marks on the surface of a component just show that the finish machining was done quickly to avoid slower feed rates that quadruple the time the part spends in the machine and thus the cost. Tune or FRM parts are finish machined yet show few tool marks because the finish machining is extremely fine, followed by polishing.

Parts with a dimpled of roughened finish have generally been finish machined to a medium standard then blasted or shot peened. Shot peening is a process where heavy, fast moving media is used to plastically deform the surface of the component. This creates a rough but hardened surface which is resistant to crack propogation.

Whether CNC maching, forging, casting or fabrication is better for one thing or another depends on a lot of factors - costs, volume, weight goals, cosmetcs, quality. Many parts use multiple operations, so it's simplistic to think that technique x is better than y. E.g. a 7900 crank uses a cold forged outer arm, to which the inner face is welded, then surfaces are machined and threads tapped, then it is finished using a variety of polishing and anodising processes. Once you understand how it's extremely impressive that Shimano bashes out thousands of them for so little cost so reliably.

I would personally not worry too much exactly how the part is made and instead concentrate on how it performs, what it looks like and how much it costs.

vmajor wrote:I really like the TRP R920 brakes. I was just admiring them the other day. After the rim and the pads "bedded in", the stopping power is awesome. They almost felt like cable pull disc brakes...on alloy rims in dry weather.

V.

+1 I have these on two bikes. Probably the most underrated brakes available, simply because they are not marketed as the "top of the line" from TRP.
A set comes in at ~260g, which is on par (or less) than a pair of Campagnolo Record Skeleton. Design is classic, mechanism top.

Also, if you can't find the TRP R920's in stock, Cane Creek (used to?) markets them as the "SL" brakes, but with different graphics. Same exact brake though.

jmartpr wrote:The C7 is practically the same weight as the CB1 but uses a whole new design that eliminates flex and improves braking power. C6 is the same design but uses a different type of alloy and SS hardware to drop the price but weight goes up at around 210 grams per set.

These look good to me... except for the logos. Anybody know if the KCNC bakes are easy to fully take apart and put back together?

Rumor has it that Jason at FWB convinced KCNC to re-do their logos on the new brakes, so stay tuned.
As for taking one part - I will find out in about a month!

What are you planning to do? I was thinking a good polishing might be nice... since the cheaper ones are 6061, I wouldn't even need to re-anodize. I'd have to remove the anodizing first (oven cleaner?) and then stick the parts in a tumbler... if I can find somebody who has one.

I'm fortunate in that the place I'm currently working for has a great working sandblaster with a mild medium in it, plus a bunch of industrial production connections which can save me a little cash here and there. The plan is to disassemble the brake, sand blast off the logo, anodize, re-assemble.

Re-assembly is the only part that has me nervous, particularly putting the spring back in as I have no experience in doing that or how to go about it, but I'm hoping I'll get some tips/help/advice when that time comes.

+1 I have these on two bikes. Probably the most underrated brakes available, simply because they are not marketed as the "top of the line" from TRP.
A set comes in at ~260g, which is on par (or less) than a pair of Campagnolo Record Skeleton. Design is classic, mechanism top.

Also, if you can't find the TRP R920's in stock, Cane Creek (used to?) markets them as the "SL" brakes, but with different graphics. Same exact brake though.

The SL's you mentioned are the ones I mentioned earlier too.... I picked them up on Ebay last year, I love 'em. Might not have the grab of a double pivot (I have the older style single pivots), but I am easy on brakes here....

Mine came in at 240g with pads.

My 2010 EE brakes have shipped so I can not wait to get them on my SLC. I like the size and the way that the housing is more to the center of the brakes. Light, strong and maybe a bit more aero.

so i ended up getting the trp's and am very impressed by the quality and they came with nice lightweight holders and swissstop pads. will post more soon.

I would recommend the EE (2010 model pictured here) as the best balance between weight, modulation and stopping power. I have replaced my KCNC CB-1 (which is lighter but weak stopping power) with the EEs and they work very well.

can we see a pic of the whole bike...

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